The illicit market in antiquities is global and huge but Interpol, the international police organization, says its true size is obscured by the privacy in which such selling takes place. Interpol adds that observers commonly rank illicit antquities as the third-largest type of black-market trafficking behind drugs and weapons.

Stanford University archaeologist Michael Shanks ventures to put a dollar sign on the trade. "Estimates vary," he says. "It's very difficult to get a handle on exactly how big the trade is, but I've heard estimates of around about four and a half to five billion dollars a year."

Artifacts became big business in the 1700's with the founding of national museums such as the British Museum in London and the Louvre in Paris. As colonial armies swept across the world, antiquities were unearthed, removed and sent back to capital cities for triumphant display. British Lord Thomas Elgin's removal of statues and other artifacts from the Parthenon in Athens two hundred years ago are a famous example of such "state collecting."

With the rise of the middle class in the 19th and early 20th centuries private individuals joined the nobility in a quest for ancient treasures. The competition among persons and museums sent prices soaring, which prompted even more opportunists to go on the hunt. Observers say the surge in personal wealth in recent decades has fueled even more illicit artifact trade. Mesopotamian civilization specialist Francis Deblauwe says certain regions are targeted. "Afghanistan is a bad one, of course. Looting in China, too. Cambodia, parts of Vietnam - it's pretty widespread."

Artifact looting and war have historically gone hand-in-hand. The most recent example is Iraq,
where the state museum in Baghdad was pillaged in April 2003 following the toppling of Saddam Hussein's government. Some of the thefts may have been an inside job, according to Neil Brodie at Cambridge University's Illicit Antiquities Research Center. "There were indications here," he says, "that these were knowledgeable as only the most valuable objects were stolen, and copies, replicas and so forth were left untouched."

Later it turned out museum employees had removed a great quantity of the artifacts for safe keeping and then returned them. Diligent police work in other countries recovered still more. U.S. authorities distributed pictures and descriptions of missing objects at all ports of entry to the country. But archaeologist Francis Deblauwe says some 85-hundred are still missing and may wind up in the hands of unscrupulous private collectors. In response, the U.S. Congress enacted a law imposing stiff penalties for unlawfully importing Iraqi artifacts, though this could have the effect of shifting sales to other countries without such prohibitions.

International agreements have been forged to control imports, exports and ownership transfers, but they are not backed by force of law. Even where laws are on the books, as in Turkey and Egypt, Mr. Deblauwe says bribes can corrupt customs officials and others. "If they're not paid enough, it is unrealistic to expect that they will really enforce the regulations." An example is a recent indictment in Egypt of ten people accused of smuggling some 57 thousand artifacts out of the country.

In the legitimate antiquities trade, ownership trails known as "provenance" are essential in order to document objects. One proposal is to give every known object a unique identification number for tracking. Interpol already maintains an extensive registry of artifacts known to be stolen or otherwise illegal, and supporters contend this system would assist authorities in spotting such objects.

Ed Able, director of the American Association of Museums, says museums have made documentation a top priority to avoid acquiring black market loot: "Museums have made it clear in their ethical statements that we do not wish to have anything in our collection that was illegally or inappropriately obtained."

Mr. Able says he speaks for the vast majority of collectors who wish to enjoy their antiquities and the history that surrounds them without the taint of illegality.